Axelrodia reisei

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A tiny South American characin, Axelrodia reisei is best known in the aquarium trade as the Ruby Tetra. Native to Colombia, it draws attention through its ruby-red coloration, which becomes more visible when the fish feels secure. This peaceful species is a schooling fish suited to calm community aquariums with dense plants and subdued lighting. The specimens offered here are wild collected, so gradual acclimation and suitable foods are especially important. With a rarity level of 1, it remains relatively accessible while being less common than the most widely distributed tetras.

General species description

Axelrodia reisei is a very small freshwater tetra associated with the Orinoco basin. Its schooling behavior is one of its main attractions: it should be kept in a group to encourage natural interaction and reduce nervousness. In a mature aquarium, it mainly uses the middle water levels, moving in short bursts between plants and shaded areas. Its temperament is generally peaceful and discreet, making it suitable for communities of small, non-aggressive fish. Its tiny size requires well-proportioned tank mates and a properly protected filter intake. Wild specimens may need time to accept dry foods; finely sized frozen foods often help with the transition. Its schooling behavior and colors are most appealing when several individuals are kept together.

Geographic origin and biotope

This species comes from Colombia, in the Orinoco basin, particularly the río Vichada area. It inhabits small streams, tributaries and quiet zones where the water may be stained by organic matter. The natural habitat combines soft water, abundant bank vegetation and light broken by branches and plant cover. Leaves, roots and woody debris may accumulate along the margins, providing shelter for small characins. The bottom is generally made up of fine sand, mud and plant debris, with low to moderate flow in sheltered areas. In the aquarium, fine-leaved plants, wood and slightly acidic to neutral water recreate this setting more successfully than a very open, brightly lit layout.

Precise location and local name

The known range of Axelrodia reisei is in Colombia, within the río Vichada basin, a tributary system of the upper Orinoco. The English common name Ruby Tetra is widely used in the aquarium trade; in French, Tétra rubis may also be encountered, while Ruby Tetra remains common in commerce. Colombian vernacular names may vary between regions and suppliers. To avoid confusion with other small red tetras, the scientific name Axelrodia reisei remains the most precise reference. Since the fish offered are wild collected, the collection origin and the quality of acclimation are important factors in their adjustment to aquarium life.

Appearance and physical characteristics

The body of Axelrodia reisei is short, slender and slightly laterally compressed. Its most distinctive feature is a ruby-red coloration that may intensify with age, condition and lighting. The fins are delicate and translucent, sometimes showing red highlights, while the eyes and body can reflect light. As with many small characins, coloration changes with stress: a newly imported fish may appear paler before recovering its color. Adult size remains very small, which makes the species suitable for a densely planted aquarium but also increases the risk of intimidation by overly active tank mates. Stable water, moderate lighting and an adequate group support the best expression of its colors and natural behavior.

General diet

In nature, Axelrodia reisei searches for tiny prey and edible particles in the water column and among vegetation. In captivity, it accepts a varied diet of quality micro-pellets, finely crushed dry foods and small frozen foods such as cyclops or baby brine shrimp. Wild specimens often benefit from a gradual transition: beginning with small frozen or live foods can stimulate feeding before dry foods are introduced progressively. Portions should be tiny and offered in small amounts so every fish can feed without excessive competition. A varied diet helps maintain the red coloration, growth and general condition while preventing uneaten food from accumulating in the aquarium.

Essential data

• River of origin: río Vichada
• Local name used: Ruby Tetra; Tétra rubis
• Origin of the scientific name: Axelrodia honors Herbert R. Axelrod; reisei is a name dedicated to Reise.
• Etymology of the full name: Axelrodia honors Herbert R. Axelrod; reisei is the specific epithet dedicated to Reise.
• Common/vernacular names: Ruby Tetra; Tétra rubis
• Family: Characidae
• Subfamily: not specified
• Name pronunciation: ax-EL-ROH-dee-ah RYE-zee-eye
• Discovery: Jacques Géry, 1960
• Maximum adult size: about 2 cm
• Water temperature and pH: 24 to 28 °C; pH 5.5 to 7.0
• Stream appearance and surrounding vegetation: small quiet streams, abundant cover, roots, wood and leaf litter
• Typical tank mates: Paracheirodon axelrodi, Hemigrammus rhodostomus, Gastrodermus hastatus
• Temperament and behavior: peaceful, schooling and rather discreet
• Water depth: shallow areas and sheltered margins
• Sexual dimorphism: mature females are generally rounder; differences are subtle
• Bottom structure and flow: sand, mud and plant debris; low to moderate flow

In your aquarium

To succeed with Axelrodia reisei, choose a mature aquarium with dense plants and subdued lighting. Keep the fish in a group, provide soft and stable water, and offer very small portions of varied food. Since these fish are wild collected, slow acclimation and close observation during the first weeks are strongly recommended. Avoid boisterous tank mates and foods that are too large. Gentle filtration, shaded areas and a few roots will help recreate its natural setting and bring out its ruby coloration.